CN113893455A

CN113893455A - Harmonic distribution of cochlear implant frequencies

Info

Publication number: CN113893455A
Application number: CN202110695096.8A
Authority: CN
Inventors: M·塞戈维亚·马丁内兹; W·诺盖拉·巴斯克斯
Original assignee: Oticon Medical AS
Current assignee: Oticon Medical AS
Priority date: 2020-06-22
Filing date: 2021-06-22
Publication date: 2022-01-07
Also published as: DK3928828T3; US20210393956A1; AU2021204182A1; EP3928828A1; EP3928828B1

Abstract

The application discloses harmonic distribution of cochlear implant frequencies, wherein a method of fitting a cochlear implant system comprises: determining an insertion angle of at least one electrode of a first electrode array of a cochlear implant system inserted into a cochlea of a patient; determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the insertion angle; determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtainable, while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies; a plurality of characteristic frequencies are assigned to each electrode of the first electrode array based on an insertion angle of the at least one electrode.

Description

Harmonic distribution of cochlear implant frequencies

Technical Field

The present invention relates to a method of fitting a cochlear implant system to a patient while preserving the harmonic relationship between cochlear implant frequencies as in the frequencies of normal hearing cochlea.

Background

With current cochlear implant fitting, the frequency allocation typically uses a standard allocation that does not take into account the physiological frequency distribution of the normal hearing cochlea.

A bimodal patient using a cochlear implant on a first ear and a conventional hearing aid providing acoustic stimulation on a second ear, and a unilateral patient with a cochlear implant on a first ear and a normal hearing of the second ear, will have a mismatch between the perception of electrical stimulation provided by the cochlear implant to the first ear and the perception of acoustic stimulation provided to the second ear with or without the conventional hearing aid. The mismatch between acoustic and electrical stimulation will be perceived by the patient as the acoustic stimulation comes from a source other than electrical stimulation.

Disclosure of Invention

An aspect of the present invention is to provide a fitting system and method of fitting a cochlear implant system to a patient that minimizes the mismatch of the way the patient perceives the electrical stimulation provided by the cochlear implant system at the first cochlea and the way the patient perceives the acoustic stimulation at the second cochlea.

Another aspect of the invention is to provide a simple way of performing the aforementioned method, which requires less computing power and fewer practical steps by the hearing aid pharmacist.

It is yet another aspect of the present invention to maintain a harmonic relationship between frequencies assigned to an electrode array for a patient using a cochlear implant system, wherein the harmonic relationship is related to natural hearing personnel.

One aspect of the invention is implemented by a method of fitting a cochlear implant system to a patient. The method comprises the following steps: an insertion angle of at least one electrode of a first electrode array of a cochlear implant system inserted into a cochlea of a patient is determined. Determining the insertion angle may be accomplished by performing diagnostic medical imaging in which the implanted electrode array and the anatomy of the cochlea are visible.

Further, the method comprises: determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the insertion angle.

The plurality of natural frequencies as a function of cochlear helix length may be determined by: determining an insertion angle for each electrode of the first electrode array based on the insertion angle determined for the at least one electrode; and mapping an insertion angle of each electrode of the first electrode array to the physiological model.

The physiological model may be based on the Greenwood model (Greenwood, 1990).

The angle of insertion of each electrode of the electrode array can be easily determined when the distance of each electrode of the electrode array is known relative to the at least one electrode for which the angle of insertion is determined.

The plurality of natural frequencies as a function of cochlear helix length may be determined by: an insertion angle of each electrode of the first electrode array is determined by performing diagnostic medical imaging in which the implanted electrode array and the anatomy of the cochlea are visible.

Further, the method comprises: a plurality of characteristic frequencies are determined as a function of cochlear helix length by frequency downshifting the plurality of natural frequencies until a target is obtainable, while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies.

In some cases it is important to retain certain perceptual information of the acoustic signal after the frequency downshifting (no frequency downshifting is done), which is achieved by introducing the goal of allowing how much frequency downshifting is allowed.

The target may be stored in a storage unit and the amount of frequency downshifting relative to the target may be stored in the storage unit.

Further, the method comprises: a plurality of characteristic frequencies are assigned to each electrode of the first electrode array based on an insertion angle of the at least one electrode. Thus, the cochlear implant system is suitable for the user.

Another aspect of the invention relates to a system for fitting a cochlear implant system to a patient, comprising: a first implantable stimulation unit having a first electrode array including a plurality of electrodes configured to apply electrical stimulation to auditory nerve fibers of a cochlea of a patient; an external unit including a memory unit including a natural frequency allocation model; a frequency allocation unit configured to allocate a plurality of characteristic frequencies to each electrode of the first electrode array according to a frequency allocation scheme.

The frequency allocation scheme includes: determining an insertion angle of at least one electrode of the first electrode array; determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the aforementioned insertion angle; determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtained while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies; and assigning a plurality of characteristic frequencies to each electrode of the first electrode array based on an insertion angle of at least one electrode.

The memory unit may be part of a cochlear implant system and/or a system for fitting a cochlear implant system.

The first implantable stimulation unit and the external unit may be part of a cochlear implant system or a fitting computer wired or wirelessly connected to the cochlear implant system. The external unit may be connected to the first implantable stimulation unit via a transcutaneous radio frequency interface applied within the external unit.

In yet another aspect, the present invention relates to a cochlear implant system that may be configured to continuously adjust multiple characteristic frequencies by dynamically changing the target. The target may depend on the acoustic signal or the sound processing procedure of the cochlear implant system. The sound processing program may be provided by an external device, such as a smart phone wirelessly connected to the cochlear implant system. Thus, the electrode array of the cochlear implant system will always have the best frequency allocation for acoustic inputs received by the cochlear implant system. The acoustic input may be received by a microphone unit or an RF antenna. The microphone unit may comprise one or more microphones.

The target may be one of:

-a characteristic frequency in a first range between 100Hz and 250Hz may be assigned to the topmost electrode of the first electrode array;

-a characteristic frequency in a second range between 6600Hz to 8100Hz may be assigned to the bottommost electrode of the first electrode array; or

-the frequency downshifting of the plurality of natural frequencies corresponds to one or more octaves.

By applying the target to the topmost electrode, important perceptual information of low frequencies is preserved after the frequency down-shift is performed.

By applying the target to the bottommost electrode, important perceptual information of high frequencies is preserved after the frequency down shift is performed.

By applying an octave limitation to the amount of frequency shift down, results in improved perceptual and tactile interpretation of the music, as the patient will perceive the music with harmonic relationships between the cochlea.

The goal may be to obtain an octave frequency shift from one electrode to another electrode of the electrode array. Thus, the patient will perceive the music better than is possible today.

The amount of frequency shift may be related to the insertion angle of the topmost electrode and the target.

Thereby, an optimal frequency allocation is obtained with respect to the position of the electrode array.

The insertion angle of the topmost electrode may be:

about 525 degrees, the frequency shift down from natural frequencies to eigenfrequencies may be between 1/3 and 1/2;

about 417 degrees, the frequency shift down from natural frequencies to eigenfrequencies may be between 1/5 and 1/2; or

About 358 degrees, the frequency shift down from natural frequencies to eigenfrequencies may be between 1/9 and 1/5.

The method may further comprise: determining an insertion angle of at least another electrode of a second electrode array of the cochlear implant system inserted into another cochlea of the patient; simultaneously and time-shifted applying stimulation pulses to at least one electrode of the first and second electrode arrays to determine a patient's binaural interaction component; and determining a plurality of natural frequencies as a function of cochlear helix length based on the binaural interaction component.

A plurality of characteristic frequencies may be determined for the first and second electrode arrays to obtain a binaural interaction component of the patient that is to be compared to a binaural interaction component of normal hearing. The binaural interaction component of normal hearing may be part of a natural frequency assignment model. The amount of frequency shift applied to the two electrode arrays may be the same or different in determining the patient's binaural interaction component. The patient's binaural interaction component is compared to the binaural interaction component for normal hearing and an acceptable matching criterion between the two binaural interaction components is determined by a standard deviation function, such as a root mean square function.

The amount of downshifting of the plurality of natural frequencies may be determined by natural binaural interaction components stored in a memory unit. The ideal amount of downshifting is the amount when the patient's binaural interaction component is similar to the natural binaural interaction component. The natural binaural interaction component may be an average of a plurality of other persons having normal hearing. Thus, the binaural interaction component is determined while adjusting the frequency down shift and stops when the binaural interaction component is similar to the natural binaural interaction component.

The binaural interaction component may be determined by the cochlear implant system or a fitting computer of the system.

The first auditory brainstem response may be recorded by recording electrodes of the first electrode array when a first stimulus is applied to the first cochlea via stimulation electrodes of the first electrode array, and the second auditory brainstem response may be recorded by recording electrodes of the second electrode array when a second stimulus is applied to the second cochlea via stimulation electrodes of the second electrode array. The second stimulation should be applied after a stimulation time from the application of the first stimulation by the first stimulation electrode for a period of time. The total auditory brainstem response is determined by summing the first auditory brainstem response and the second auditory brainstem response. Alternatively, the second auditory brainstem response may be time-shifted by an interaural time difference relative to the first auditory brainstem response prior to summing. Then, when stimulation pulses are applied simultaneously via the stimulation electrodes of the first and second electrode arrays, a binaural waveform is recorded by the first and second electrode arrays or by external electrodes applied on the head and located between the ears of the patient's head. The binaural interaction component is determined by subtracting the binaural waveform and the total auditory brainstem response.

The method can comprise the following steps: determining another insertion angle of at least another electrode of the second electrode array; simultaneously and time-shifted applying stimulation pulses to at least one electrode of the first and second electrode arrays to determine a patient's binaural interaction component; determining a plurality of natural frequencies and another plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model, binaural interaction component, the insertion angle, and another insertion angle, respectively; determining a plurality of characteristic frequencies as a function of the cochlear spiral length by frequency-downshifting a plurality of natural frequencies until the target is obtained, determining another plurality of characteristic frequencies as a function of the cochlear spiral length by frequency-downshifting another plurality of natural frequencies until the target is obtained, while preserving harmonic relationships between the natural frequencies of the plurality of natural frequencies and the another plurality of natural frequencies among the plurality of characteristic frequencies and the another plurality of characteristic frequencies, respectively; a plurality of characteristic frequencies and another plurality of characteristic frequencies are assigned to each electrode of the first and second electrode arrays, respectively.

Thus, the patient will experience improved binaural information perception in a bilateral cochlear implant system, as the frequency assigned to each electrode of the first and second electrode arrays will be optimized to the extent of how normal hearing persons perceive binaural information.

The method can comprise the following steps: simultaneously and time-shifted applying a stimulation pulse to at least one electrode of the first electrode array and applying acoustic stimulation to another cochlea of the patient to determine binaural interaction components of the patient, a plurality of natural frequencies based on the binaural interaction components as a function of cochlear helix length is determined.

The method can comprise the following steps: simultaneously and time-displaced applying a stimulation pulse via the hearing aid to at least one electrode of the first electrode array and applying acoustic stimulation to the other cochlea to determine binaural interaction components of the patient; determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model, binaural interaction components, and insertion angle; determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtained while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies; and respectively allocating a plurality of characteristic frequencies to each electrode of the first electrode array.

Thus, the patient will experience improved binaural information perception in the bi-modal cochlear implant system, as the frequency assigned to each electrode of the first electrode array will be optimized to the extent of how the normal hearing person perceives the binaural information.

Cochlear implant systems may be of the bilateral type, which includes an electrode array in each of the patient's two cochlea.

The cochlear implant system may be a dual mode type, which includes an electrode array in one cochlea and a hearing aid in another cochlea of the patient.

The binaural interaction component may comprise a plurality of local maxima at different local maximum frequencies. The amount of frequency shift may be determined by a harmonic relationship between different local maximum frequencies relative to a harmonic relationship between the plurality of natural frequencies. The amount of frequency downshifting is best when the harmonic relationship between different local maximum frequencies is similar to the harmonic relationship between natural frequencies of multiple natural frequencies.

The method can comprise the following steps: determining an insertion angle of at least another electrode of a second electrode array of the cochlear implant system inserted into another cochlea of the patient; applying a stimulation pulse to at least one electrode of the first and second electrode arrays to determine an interaural pulse time difference sensitivity or an interaural pitch match of the patient; and determining a plurality of natural frequencies as a function of cochlear helix length based on interaural pulse time difference sensitivity or interaural pitch matching.

The system may include a filter bank configured to generate a plurality of audio bands, wherein each of the plurality of audio bands is mapped to each electrode of the electrode array, and wherein a frequency range of each of the plurality of audio bands includes at least a plurality of characteristic frequencies assigned to the respective mapped electrode.

The memory unit of the cochlear implant system may include a plurality of targets for respective acoustic environments detectable by the microphone unit or the RF antenna. Thus, the cochlear implant system is configured to continuously optimize the allocation of multiple characteristic frequencies for which acoustic environment the patient is within.

The cochlear implant system may be configured to receive a setup signal from an external device, such as a smartphone, via the RF antenna of the cochlear implant system, or the setup signal may be provided by the cochlear implant system by analyzing the acoustic signal. The setup signal may be used by the cochlear implant system to select a sound processing program that the external unit may use to determine an optimal sampling and/or encoding strategy for the acoustic signal, whereby the external unit determines an amount of frequency downshifting and a natural frequency assignment model for obtaining an optimal assignment of a plurality of characteristic frequencies based on the sampling and encoding strategy. The sampling and/or encoding may be performed by a sound processor of the external device.

The setting signal may be provided by a sound processor of the external device, which is configured to analyze the encoded acoustic signal to determine at least a fundamental frequency and/or a harmonic frequency. At least the base frequency may be a setting signal for determining the amount of frequency down shift and selecting a natural frequency allocation model from memory.

The setup signal may be determined by the patient via an external device or by a server connected to the external device, which uses the external device as an intermediary device for communicating with the cochlear implant system.

The setting signal may be automatically determined by an envelope analyzer of the external unit, which determines the acoustic environment in combination with the microphone unit or the RF antenna.

The external unit may be a sound processor applied on the patient's head, magnetically attracted by the implantable stimulation unit via the magnetic interface. Furthermore, the external unit may be applied on the ear. The implantable stimulation unit and the external unit are configured to communicate with each other via a transcutaneous radio frequency link.

The cochlear implant system may be fully implantable.

The method may be performed by a fitting computer and/or cochlear implant system and/or external device such as smart phone, tablet, etc.

In another aspect, a method of fitting a cochlear implant system to a patient may comprise: determining an insertion angle of at least one electrode of a first electrode array of a cochlear implant system inserted into a cochlea of a patient; determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and an insertion angle; determining a plurality of characteristic frequencies as a function of cochlear helix length while preserving harmonic relationships between natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies; and assigning a plurality of characteristic frequencies to each electrode of the first electrode array based on an insertion angle of at least one electrode.

Thus, a mismatch between the way the patient perceives the electrical stimulation provided by the cochlear implant system at the first cochlea and the way the patient perceives the acoustic stimulation at the second cochlea is minimized.

Drawings

Various aspects of the invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings. For the sake of clarity, the figures are schematic and simplified drawings, which only show details which are necessary for understanding the invention and other details are omitted. Throughout the specification, the same reference numerals are used for the same or corresponding parts. The various features of each aspect may be combined with any or all of the features of the other aspects. These and other aspects, features and/or technical effects will be apparent from and elucidated with reference to the following figures, in which:

fig. 1 illustrates a method of fitting a cochlear implant system;

FIGS. 2A and 2B show the position of the electrode array and the frequency downshifting of multiple natural frequencies;

FIG. 3 illustrates a frequency downshifting of a plurality of natural frequencies;

fig. 4A and 4B illustrate a determination method for determining binaural interaction components;

fig. 5A, 5B, and 5C illustrate different examples of systems for fitting cochlear implant systems;

fig. 6 shows a cochlear implant system.

Detailed Description

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. It will be apparent, however, to one skilled in the art that these concepts may be practiced without these specific details. Several aspects of the apparatus and methods are described in terms of various blocks, functional units, modules, elements, etc. (collectively referred to as "elements"). These elements may be implemented with other equivalent elements depending on the particular application, design constraints, or other reasons.

The hearing aid is adapted to improve or enhance the hearing ability of a user by receiving acoustic signals from the user's environment, generating corresponding audio signals, possibly modifying the audio signals, and providing the possibly modified audio signals as audible signals to at least one ear of the user. The audible signal may be provided in the form of: an acoustic signal that is transmitted as a mechanical vibration through the bone structure of the user's head to the user's inner ear.

The hearing aid is adapted to be worn in any known manner. This may comprise arranging the unit of the hearing aid to be connected to a fixation structure implanted in the skull bone, for example in a bone anchored hearing aid, or at least a part of the hearing aid may be an implanted part.

"hearing system" or "cochlear implant system" refers to a system that includes one or two hearing aids or one or two cochlear implants. "binaural hearing system" refers to a system comprising two hearing aids or two cochlear implants, wherein the hearing aids are adapted to provide audible signals to both ears of a user in cooperation, or a bone conduction type hearing aid or an acoustic hearing aid may be part of a bimodal system comprising a cochlear implant and a hearing aid or a bone conduction hearing aid. The system may further comprise an external device communicating with at least one hearing aid, the external device influencing the operation of the hearing aid and/or benefiting from the function of the hearing aid. A wired or wireless communication link is established between at least one hearing aid and an external device to enable information (such as control and status signals, possibly audio signals) to be exchanged therebetween. The external device may include at least one of: a remote control, a remote microphone, an audio gateway device, a mobile phone, a broadcast system, a car audio system, a music player, or a combination thereof. The audio gateway device is adapted to receive a plurality of audio signals, such as from an entertainment apparatus, such as a TV or a music player, from a telephone apparatus, such as a mobile phone, or from a computer, such as a PC. The audio gateway device is further adapted to select and/or combine appropriate ones of the received audio signals (or signal combinations) for transmission to the at least one hearing aid. The remote control is adapted to control the function and operation of at least one hearing aid. The functionality of the remote control may be implemented in a smart phone or another electronic device, which may run an application controlling the functionality of at least one hearing aid.

Generally, a hearing aid or cochlear implant comprises i) an input unit, such as a microphone, for receiving acoustic signals from around the user and providing corresponding input audio signals; and/or ii) a receiving unit for electronically receiving an input audio signal. The hearing aid further comprises a signal processing unit for processing the input audio signal and an output unit for providing an audible signal to the user in dependence of the processed audio signal.

The input unit may comprise a plurality of input microphones, for example for providing direction dependent audio signal processing. The aforementioned directional microphone system is adapted to enhance a target sound source of a plurality of sound sources in a user's environment. In one aspect, the directional system is adapted to detect (e.g. adaptively detect) from which direction a particular part of the microphone signal originates. This can be achieved using conventionally known methods. The signal processing unit may comprise an amplifier adapted to apply a frequency dependent gain to the input audio signal. The signal processing unit may also be adapted to provide other suitable functions such as compression, noise reduction, etc. The output unit may comprise an output transducer for providing mechanical vibrations to the skull bone percutaneously or transdermally.

Fig. 1 shows a method 100 of fitting a cochlear implant system 200 to a patient. The method comprises the following steps: at step 102, determining an insertion angle of at least one electrode of a first electrode array of a cochlear implant system inserted into a cochlea of a patient; determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the insertion angle, step 104; determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtained while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies, at step 106; at step 108, a plurality of characteristic frequencies are assigned to each electrode of the first electrode array based on the insertion angle of the at least one electrode.

The method 100 may also include: at step 102, determining an insertion angle for each electrode of the first electrode array based on the insertion angle determined for at least one electrode; at step 104, a plurality of natural frequencies as a function of cochlear helix length is determined by mapping the insertion angle of each electrode of the first electrode array to a physiological model.

The method 100 may also include: at step 102, determining an insertion angle of at least another electrode of a second electrode array of the cochlear implant system inserted into another cochlea of the patient; applying a stimulation pulse to at least one electrode of the first and second electrode arrays to determine a binaural interaction component of the patient at step 103; and determining a plurality of natural frequencies as a function of cochlear helix length based on the binaural interaction component at step 104.

The method 100 may also include: at step 102, determining an insertion angle of at least another electrode of a second electrode array of the cochlear implant system inserted into another cochlea of the patient; applying a stimulation pulse to at least one electrode of the first and second electrode arrays to determine an interaural pulse time difference sensitivity or an interaural pitch match at step 103; and determining a plurality of natural frequencies as a function of cochlear helix length based on interaural pulse time difference sensitivity or interaural pitch matching, at step 104.

Fig. 2A shows the position of the electrode array 2 within the cochlea 10 of a patient of a cochlear implant system, such as a first electrode array or a second electrode array. In this particular example, the bottommost electrode 3a and the topmost electrode 3b are seen within the cochlea 10. In this example, the insertion angle may be determined for the topmost electrode 3b or the bottommost electrode 3 a. The electrode for which the insertion angle is determined may be any electrode 3. Fig. 2B shows an example of a frequency downshifting 24 of a plurality of natural frequencies 20 to determine a plurality of characteristic frequencies 22. The frequency range covered by the electrode array 2 is determined by the position of the electrode array 2 within the cochlea 10. In this example, the lowest frequency range 21a of the plurality of characteristic frequencies 22 is assigned to the apical-most electrode 3b, and the highest frequency range 21b of the plurality of characteristic frequencies 22 is assigned to the basal-most electrode 3a disposed within the cochlea 10. The remaining electrodes 3 of the electrode array 2 may be assigned the remaining frequency ranges (21, not shown) of the plurality of characteristic frequencies 22 based on the insertion angle.

Table 1 shows different examples of placement of the apical-most electrode 3b within the cochlea 10. When the insertion angle of the topmost electrode 3b is 525 degrees, the minimum natural frequency assigned to the electrode 3b is 300 Hz. This means that the topmost electrode does not cover a frequency range below 300 Hz. When the insertion angle of the topmost electrode 3b is 417 degrees, the minimum natural frequency assigned to the electrode 3b is 500 Hz. This means that the topmost electrode does not cover a frequency range below 500 Hz. When the insertion angle of the topmost electrode 3b is 358 degrees, the minimum natural frequency assigned to the electrode 3b is 900 Hz. This means that the topmost electrode does not cover the frequency range below 900 Hz.

TABLE 1

The amount of frequency shift is determined by the ratio 1/N, which is related to the plurality of natural frequencies (20, fn)_c0) Multiplying to determine a plurality of eigenfrequencies (22, fci)_c0)。

Table 2 shows an example in which the natural frequency of the topmost electrode 3b is shifted down in the ratio between 1/3 and 1/2 at an insertion angle of the topmost electrode of 525 degrees so as to obtain the minimum characteristic frequency between 100Hz and 150 Hz. This is also true when the insertion angles are 417 degrees and 358 degrees, but as the insertion angle of the topmost electrode 3b decreases, the ratio 1/N increases incrementally.

TABLE 2

Fig. 3 shows an example where the frequency downshifting 24 corresponds to one or more octaves. The frequency downshifting 24 results in an octave frequency shift from one electrode of the electrode array to another, e.g., an adjacent electrode. In this example, the frequency down shift corresponds to a single octave, which means, for example, that for a given electrode 2, the tone "B5" is shifted down to the tone "B4". In another example, the frequency downshifting may be two octaves, meaning that tone "B5" is downshifted to tone "B3", and so on.

Fig. 4A and 4B show examples of how the binaural interaction component of a patient is determined and how a plurality of natural frequencies as a function of cochlear helix length are determined based on the binaural interaction component. Fig. 4A, scenario a, shows a fitting scenario in which a first auditory brainstem response ABR1 is recorded by recording electrodes of a first electrode array 2a when a first stimulus is applied to the first cochlea via stimulation electrodes of the first electrode array. In scenario B, a second auditory brainstem response ABR2 is recorded by a recording electrode (or electrode probe) of the second electrode array 2B as a second stimulus is applied to the second cochlea via the stimulation electrodes of the second electrode array 2B. Alternatively, in scene B, the second auditory brainstem response ABR2 is recorded by a recording probe applied in the ear canal of the ear opposite the ear to which the electrical stimulation was applied, when the acoustic stimulation was applied by the speaker of the hearing aid to the second cochlea. The second stimulus or acoustic stimulus should be applied after a stimulation time from the application of the first stimulus by the first stimulation electrode by a time period. The total auditory brainstem response ABR is determined by summing a first auditory brainstem response ABR1 and a second auditory brainstem response ABR 2. Alternatively, prior to summing, the second auditory brainstem response ABR2 may be time-shifted by an interaural time difference ITD relative to the first auditory brainstem response. Then, when simultaneously applying stimulation pulses via the stimulation electrodes of the first and second electrode arrays (2a,2b) or when simultaneously applying stimulation pulses and acoustic stimulation, the binaural waveform BI is recorded by the first and second electrode arrays (2a,2b), or by the first electrode array and the microphone of the hearing aid, or by the external electrode 30 applied on the head and located between the ears of the patient's head. The binaural interaction component BIC was determined by subtracting the binaural waveform BI and the total auditory brainstem response ABR. The external electrodes may be EEG electrodes 30.

Fig. 4B shows an example of determining a plurality of characteristic frequencies for each electrode array (2a,2B) to obtain a patient's binaural interaction component BIC-CI similar or comparable to the binaural interaction component BIC-NH of a normal hearing person. In scenario a of fig. 4B, a match of the difference between BIC-CI and BIC-NH is seen for a given amount of frequency downshifting for multiple natural frequencies for the two electrode arrays (2a,2B) or only for the first electrode array 2 a. In scenario B of FIG. 4B, a better match between BIC-CI and BIC-NH is seen for a given amount of frequency downshifting. Scenario C of fig. 4B shows an acceptable match between BIC-CI and BIC-NH for a given amount of frequency downshifting. The acceptable matching criterion may be determined by a standard deviation function, such as a root mean square function. Acceptable matching criteria can be determined by the harmonic relationship between the local maxima present in the BIC-CI.

The amount of frequency shift down may be the same or different between the electrode arrays (2a,2 b).

Fig. 5A and 5B illustrate a system 300 for fitting a cochlear implant system 200 to a patient. In this particular example, the system 300 includes: a first implantable stimulation unit 202 having a first electrode array 2b including a plurality of electrodes 3 configured to apply electrical stimulation to auditory nerve fibers of a patient cochlea 10. System 300 also includes an external unit (204,302) that includes memory unit 208 that includes a natural frequency assignment model. In this particular example, the external unit may be the fitting computer 302 and/or the sound processor 204 applied on the user's head or implanted with the implantable stimulation unit 202. The system 300 further comprises a frequency allocation unit 210 configured to allocate a plurality of characteristic frequencies 22 to each electrode 3 of the first electrode array 2b according to a frequency allocation scheme. The frequency allocation unit may be provided within the fitting computer 302 and/or the sound processor 204. The frequency allocation scheme includes:

-determining an insertion angle of at least one electrode of the first electrode array 2 b;

determining a plurality of natural frequencies 20 as a function of the cochlear spiral length based on the natural frequency assignment model and the aforementioned insertion angle;

determining a plurality of characteristic frequencies 22 as a function of cochlear spiral length by frequency-downshifting 24 the plurality of natural frequencies 20 until a target is obtained, while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies 20 among the plurality of characteristic frequencies 22; and

assigning a plurality of characteristic frequencies 22 to each electrode 3 of the first electrode array 2b based on the insertion angle of at least one electrode (3,3a,3 b).

In fig. 5A, if the method 100 is performed by the fitting computer 302, the fitting computer 302 is connected to the cochlear implant system 200. In another scenario where method 100 is performed by cochlear implant system 200, a connection to fitting computer 302 is not necessary. Similar to the system 300 shown in fig. 5B and 5C.

In fig. 5B, system 300 includes a first cochlear implant system 200a, a second cochlear implant system 200B, and optionally EEG electrodes 30 connected to a fitting computer 302. The system 300 is configured to determine a binaural interaction component BIC of the patient in the bilateral configuration. A method of fitting a cochlear implant system is described in conjunction with fig. 4A and 4B.

In fig. 5C, the system 300 includes the first cochlear implant system 200a, the hearing aid 400, and optionally the EEG electrodes 30 connected to the fitting computer 302. The system 300 is configured to determine a binaural interaction component BIC of the patient in the bi-modal configuration. A method of fitting a cochlear implant system is described in conjunction with fig. 4A and 4B.

Fig. 6 shows a cochlear implant system 200 that includes a sound processor 204, a microphone 206, a memory unit 208, a frequency assignment unit 210, and a transcutaneous radio frequency link 212 configured to inductively communicate with an implantable stimulation unit 202 connected to the electrode array 2. In this example, the cochlear implant system is configured to continuously adjust the plurality of characteristic frequencies by dynamically changing the target. The target may depend on the acoustic signal or the sound processing procedure of the cochlear implant system. The sound processing program may be provided through an external device 214, such as a smart phone that is wirelessly connected to the cochlear implant system 200. Thus, the electrode array of the cochlear implant system will always have the best frequency allocation for acoustic input received through the microphone unit 206 or RF antenna (not shown). The microphone unit 206 may include one or more microphones.

The cochlear implant system 200 includes a filter bank 216 configured to generate a plurality of audio bands, wherein each of the plurality of audio bands is mapped to each electrode 3 of the electrode array 2, and wherein the frequency range of each of the plurality of audio bands includes at least a plurality of characteristic frequencies 22 assigned to the respective mapped electrode 3.

As used herein, the singular forms "a", "an" and "the" include plural forms (i.e., having the meaning "at least one"), unless the context clearly dictates otherwise. It will be further understood that the terms "has," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, components, and/or steps, but do not preclude the presence or addition of one or more other features, elements, components, and/or steps. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present, unless expressly stated otherwise. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

It should be appreciated that reference throughout this specification to "one embodiment" or "an aspect" or "may" include features means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the invention. The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects.

The scope of the invention should be determined with reference to the claims.

Claims

1. A method of fitting a cochlear implant system, the method comprising:

determining an insertion angle of at least one electrode of a first electrode array of a cochlear implant system inserted into a cochlea of a patient;

determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the insertion angle;

determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtainable, while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies;

a plurality of characteristic frequencies are assigned to each electrode of the first electrode array based on an insertion angle of the at least one electrode.

2. The method of fitting a cochlear implant system of claim 1, wherein the target is one of:

a characteristic frequency in a first range between 100Hz to 250Hz is assigned to the topmost electrode of the first electrode array;

a characteristic frequency in a second range between 6600Hz to 7700Hz is assigned to a bottommost electrode of the first electrode array; or

The frequency downshifting of the plurality of natural frequencies corresponds to an octave.

3. The method of fitting a cochlear implant system of claim 1, wherein the amount of frequency shift down is related to the angle of insertion of the apical-most electrode and the target.

4. The method of fitting a cochlear implant system according to any of the preceding claims, wherein the insertion angle of the topmost electrode is:

about 525 degrees, the frequency shift from the plurality of natural frequencies to the plurality of eigenfrequencies is between 1/3 and 1/2;

about 417 degrees, with a frequency shift from multiple natural frequencies to multiple eigenfrequencies down between 1/5 and 1/2; or

Approximately 358 degrees, the frequency shift from natural frequencies to eigenfrequencies is between 1/9 and 1/5.

5. The method of fitting a cochlear implant system of claim 1, comprising:

determining an insertion angle for each electrode of a first electrode array based on the insertion angle determined for the at least one electrode;

a plurality of natural frequencies as a function of cochlear helix length is determined by mapping the insertion angle of each electrode of the first electrode array to a physiological model.

6. The method of fitting a cochlear implant system of any of claims 1-3, wherein the method comprises:

determining an insertion angle of at least another electrode of a second electrode array of the cochlear implant system inserted into another cochlea of the patient;

simultaneously and time-shifted applying stimulation pulses to at least one electrode of the first and second electrode arrays to determine a patient's binaural interaction component; and

a plurality of natural frequencies are determined as a function of cochlear helix length based on the binaural interaction component.

7. The method of fitting a cochlear implant system of any of claims 1-3, wherein the method comprises:

applying a stimulation pulse to at least one electrode of the first and second electrode arrays to determine an interaural pulse time difference sensitivity or an interaural pitch match; and

a plurality of natural frequencies are determined as a function of cochlear helix length based on interaural pulse time difference sensitivity or interaural pitch matching.

8. A system for fitting a cochlear implant system, comprising:

a first implantable stimulation unit having a first electrode array including a plurality of electrodes configured to apply electrical stimulation to auditory nerve fibers of a cochlea of a patient;

an external unit including a memory unit including a natural frequency allocation model;

a frequency allocation unit configured to allocate a plurality of characteristic frequencies to each electrode of the first electrode array according to a frequency allocation scheme, wherein the frequency allocation scheme comprises:

determining an insertion angle of at least one electrode of the first electrode array;

determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model and the aforementioned insertion angle;

determining a plurality of characteristic frequencies as a function of cochlear spiral length by frequency-downshifting the plurality of natural frequencies until a target is obtained while preserving a harmonic relationship between the natural frequencies of the plurality of natural frequencies among the plurality of characteristic frequencies; and

a plurality of characteristic frequencies are assigned to each electrode of the first electrode array based on an insertion angle of at least one electrode.

9. The system for fitting a cochlear implant system according to claim 8, comprising a filter bank configured to generate a plurality of audio bands, wherein each of the plurality of audio bands is mapped to each electrode of the electrode array, and wherein the frequency range of each of the plurality of audio bands includes at least a plurality of characteristic frequencies assigned to the respective mapped electrode.

10. The system for fitting a cochlear implant system of claim 8, wherein the target is one of:

a characteristic frequency in a second range between 6600Hz to 8100Hz is assigned to a bottommost electrode of the first electrode array; or

11. The system for fitting a cochlear implant system of claim 8, wherein the amount of frequency shift down is related to the angle of insertion of the apical-most electrode and the target.

12. The system for fitting a cochlear implant system of claim 11, wherein the insertion angle of the most apical electrode is:

13. The system for fitting a cochlear implant system of claim 8, wherein the plurality of natural frequencies as a function of cochlear spiral length is determined by mapping a location of each electrode of the first electrode array to a physiological model based on the determined insertion angle of the at least one electrode.

14. The system for fitting a cochlear implant system according to any of claims 8-13, comprising a second implantable stimulation unit having a second electrode array comprising a plurality of electrodes configured to apply electrical stimulation to auditory nerve fibers of another cochlea of the patient, and wherein the frequency allocation scheme comprises:

15. The system for fitting a cochlear implant system according to any of claims 8-13, comprising a hearing aid configured to apply acoustic stimulation to auditory nerve fibers of another cochlea of the patient, and wherein the frequency assignment scheme comprises:

simultaneously and time-displaced applying a stimulation pulse via the hearing aid to at least one electrode of the first electrode array and applying acoustic stimulation to the other cochlea to determine binaural interaction components of the patient;

determining a plurality of natural frequencies as a function of cochlear helix length based on a natural frequency assignment model, binaural interaction components, and insertion angle;

a plurality of characteristic frequencies are respectively assigned to each electrode of the first electrode array.